#ifndef CONSTANTS_H
#define CONSTANTS_H
#include <cmath>

#ifdef PI
const double PI = PI;
#else
const double PI = 3.1415926535;
#endif

const double PI_2 = PI*2.0;
#define PI_DIV_2 1.57079632679489661923
#define PI_DIV_4 0.78539816339744830961;

const double DEGREES_TO_RADIANS = PI/180.0;
const double RADIANS_TO_DEGREES = 180.0/PI;

#define E 2.7182818284590452354

/** pi/180/60/60, or about 100 feet at earths' equator */
#define EARTH_ONE_SECOND 4.848136811E-6

/** Radius of Earth in kilometers at the equator.  Another source had
 *  6378.165 but this is probably close enough */
#define EARTH_RAD 6378.155

 // Maximum terrain elevation from sea level
#define SMAX_ELEVATION_M 9000.0

// Earth parameters for WGS 84, taken from LaRCsim/ls_constants.h

/** Value of earth radius from LaRCsim (ft) */
#define EQUATORIAL_RADIUS_FT  20925650.

/** Value of equatorial earth radius from LaRCsim (meter) */
#define EQUATORIAL_RADIUS_M   6378138.12

/** Radius squared (ft) */
#define EQ_RAD_SQUARE_FT 437882827922500.

/** Radius squared (meter) */
#define EQ_RAD_SQUARE_M   40680645877797.1344

/** Value of WGS84 polar earth radius (meter) */
#define POLAR_RADIUS_M   6356752.3142451794975639668

// Physical Constants, SI

/**mean gravity on earth */
#define g0_m_p_s2          9.80665   // m/s2

/**standard pressure at SL */
#define p0_Pa              101325.0 // Pa

/**standard density at SL */
#define rho0_kg_p_m3       1.225 // kg/m3

/**standard temperature at SL */
#define T0_K               288.15   // K (=15degC)

/**specific gas constant of air*/
#define R_m2_p_s2_p_K      287.05   // m2/s2/K

/**specific heat constant at constant pressure*/
#define cp_m2_p_s2_p_K 1004.68      // m2/s2/K   

/**ratio of specific heats of air*/
#define SDK_gamma              1.4         // =cp/cv (cp = 1004.68 m2/s2 K , cv = 717.63 m2/s2 K)

/**constant beta used to calculate dynamic viscosity */
#define SDK_beta_kg_p_sm_sqrK  1.458e-06   // kg/s/m/SQRT(K) 

/** Sutherland constant */
#define SDK_S_K                110.4       // K

// Conversions

/** Arc seconds to radians.  (arcsec*pi)/(3600*180) = rad */
#define SDK_ARCSEC_TO_RAD    4.84813681109535993589e-06 

/** Radians to arc seconds.  (rad*3600*180)/pi = arcsec */
#define SDK_RAD_TO_ARCSEC    206264.806247096355156

/** Feet to Meters */
#define SDK_FEET_TO_METER    0.3048

/** Meters to Feet */
#define SDK_METER_TO_FEET    3.28083989501312335958  

/** Meters to Nautical Miles.  1 nm = 6076.11549 feet */
#define SDK_METER_TO_NM      0.0005399568034557235

/** Nautical Miles to Meters */
#define SDK_NM_TO_METER      1852.0000

/** Meters to Statute Miles. */
#define SDK_METER_TO_SM      0.0006213699494949496

/** Statute Miles to Meters. */
#define SDK_SM_TO_METER      1609.3412196

/** Radians to Nautical Miles.  1 nm = 1/60 of a degree */
#define SDK_NM_TO_RAD        0.00029088820866572159

/** Nautical Miles to Radians */
#define SDK_RAD_TO_NM        3437.7467707849392526

/** meters per second to Knots */
#define SDK_MPS_TO_KT        1.9438444924406046432

/** Knots to meters per second */
#define SDK_KT_TO_MPS        0.5144444444444444444

/** Feet per second to Knots */
#define SDK_FPS_TO_KT        0.5924838012958962841

/** Knots to Feet per second */
#define SDK_KT_TO_FPS        1.6878098571011956874

/** meters per second to Miles per hour */
#define SDK_MPS_TO_MPH       2.2369362920544020312

/** meetrs per hour to Miles per second */
#define SDK_MPH_TO_MPS       0.44704

/** Meters per second to Kilometers per hour */
#define SDK_MPS_TO_KMH       3.6

/** Kilometers per hour to meters per second */
#define SDK_KMH_TO_MPS       0.2777777777777777778

/** Pascal to Inch Mercury */
#define SDK_PA_TO_INHG       0.0002952998330101010

/** Inch Mercury to Pascal */
#define SDK_INHG_TO_PA       3386.388640341

/** slug/ft3 to kg/m3 */
#define SDK_SLUGFT3_TO_KGPM3   515.379

/** For divide by zero avoidance, this will be close enough to zero */
#define SDK_EPSILON 0.0000001

#endif
